The use of a portable device equipped with a flexible display is increasing. In this case, the portable device equipped with the flexible display can provide a user with a wide screen. At the same time, the portable device equipped with the flexible display may have a foldable structure. With the help of the foldable structure, portability of the portable device can be enhanced. Recently, a portable device including three foldable bodies is proposed. In this case, the portable device may operate in a state that all bodies are folded. And, the portable device may operate in a state that all bodies are unfolded. In this case, an operation method of the portable device can be differently configured according to a folded state of the body. Hence, it is necessary to have a method of controlling the operation method.